Biodegradable mulch film is a ground cover material designed for agricultural use that naturally breaks down in the soil. Farmers use this film to cover the soil surface around crops. Its purpose is to provide benefits similar to traditional plastic mulches, but without leaving behind persistent plastic waste. This material offers an environmentally sound approach to crop protection and soil management.
Understanding Biodegradable Mulch Film Composition and Breakdown
Biodegradable mulch films are made from a combination of plant-based polymers and synthetic polyesters. Plant-based components include starches, cellulose, and polyhydroxyalkanoates (PHA), derived from microbes or plants. Synthetic polyesters like poly(butylene adipate-co-terephthalate) (PBAT), polylactic acid (PLA), and poly(butylene succinate) (PBS) are used in their manufacture. These materials are selected for their ability to break down under specific environmental conditions.
The breakdown process of these films in the soil is driven by microbial activity. Soil microorganisms, such as bacteria and fungi, produce enzymes that break down the polymer chains into smaller molecules. These smaller molecules are then metabolized by the microbes, converting the film into water, carbon dioxide, and biomass. This process is distinct from photodegradation, which relies on sunlight, or oxo-degradation, which involves chemical oxidation and can leave behind microplastic fragments.
The rate of degradation can vary depending on factors like soil temperature, moisture levels, and the specific microbial community present. These films are designed to maintain their integrity throughout the growing season and then begin to break down once tilled into the soil after harvest. This ensures they provide agronomic benefits while the crop is growing, and then integrate back into the natural soil cycle.
Agricultural and Environmental Advantages
Biodegradable mulch film offers several advantages for crop production. It suppresses weed growth, reducing the need for herbicides and minimizing competition for nutrients and water. The film also retains soil moisture by reducing evaporation from the soil surface, leading to more efficient water use. It can also regulate soil temperature, promoting earlier crop development and a faster growth rate.
Beyond direct crop benefits, biodegradable mulch films provide environmental advantages. Unlike traditional plastic mulches, they do not need to be removed from the field after the growing season, eliminating labor and disposal costs. This reduces the accumulation of plastic waste in agricultural soils, addressing a growing concern about plastic pollution. As the film breaks down, it contributes to the soil’s organic matter, potentially improving soil health and microbial activity over time.
Real-World Applications and Practical Use
Biodegradable mulch film is applied in various agricultural settings, particularly for specialty crops. It is used for growing vegetables such as tomatoes, peppers, and melons, as well as fruits like strawberries. These films find use in both open-field row cropping and in protected environments like greenhouses, where they manage soil conditions for plant growth.
Farmers apply biodegradable mulch film using specialized equipment, similar to how traditional plastic mulch is laid. The film is unrolled and secured onto prepared beds, often with the edges buried in the soil. The expected lifespan of these films in the field is designed to match the typical growing season of the crops they support, usually ranging from 3 to 6 months. After harvest, the film can be tilled directly into the soil, where it begins its biodegradation process.
Proper handling and storage ensure the film’s effectiveness. It should be stored in a cool, dry place away from direct sunlight to prevent premature degradation or damage before application. While the material is designed to break down, its integrity during the growing cycle is maintained through its specific polymer composition and manufacturing process.
Comparing Biodegradable and Traditional Plastic Mulch
Biodegradable mulch film differs from traditional polyethylene (PE) plastic mulch in its material composition. Traditional plastic mulch is made from low-density polyethylene, a non-biodegradable polymer derived from fossil fuels. In contrast, biodegradable films are composed of plant-based polymers or specific synthetic polyesters that break down in the soil.
Disposal methods represent a distinction between the two types of mulch. Traditional plastic mulch must be removed from the field after use, which is a labor-intensive and costly process. This removed plastic often ends up in landfills or requires energy-intensive recycling processes, and even then, fragments can persist. Biodegradable mulch films, however, are designed to be tilled into the soil after the growing season, where they naturally biodegrade into harmless components, eliminating removal and reducing plastic pollution.
Regarding environmental impact, traditional plastic mulch contributes to microplastic and macroplastic accumulation in agricultural soils, which can negatively affect soil properties and microbial communities. Biodegradable films mitigate this pollution by fully breaking down, potentially enhancing soil health by enriching microbial activity. While traditional plastic mulch can be cheaper upfront, the long-term costs of removal and disposal can make biodegradable options more economically viable over time.